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DDC: 530 × Has files: Yes × search.filters.applied.f.series: New Journal of Physics, Volume 11 × Subject: Antiferromagnetics ×

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    Electronic structure and magnetic properties of the spin-1/2 Heisenberg system CuSe2O5
    (Milton Park : Taylor & Francis, 2009) Janson, O.; Schnelle, W.; Schmidt, M.; Prots, Yu; Drechsler, S.-L.; Filatov, S.K.; Rosner, H.
    A microscopic magnetic model for the spin-1/2 Heisenberg chain compound CuSe2O5 is developed based on the results of a joint experimental and theoretical study. Magnetic susceptibility and specific heat data give evidence for quasi-one-dimensional (1D) magnetism with leading antiferromagnetic (AFM) couplings and an AFM ordering temperature of 17 K. For microscopic insight, full-potential density functional theory (DFT) calculations within the local density approximation (LDA) were performed. Using the resulting band structure, a consistent set of transfer integrals for an effective one-band tight-binding model was obtained. Electronic correlations were treated on a mean-field level starting from LDA (LSDA+U method) and on a model level (Hubbard model). With excellent agreement between experiment and theory, we find that only two couplings in CuSe2O5 are relevant: the nearest-neighbour intra-chain interaction of 165 K and a non-frustrated inter-chain (IC) coupling of 20 K. From a comparison with structurally related systems (Sr2Cu(PO4)2, Bi2CuO4), general implications for a magnetic ordering in presence of IC frustration are made.
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    Domain wall asymmetries in Ni81Fe19/NiO: Proof of variable anisotropics in exchange bias systems
    (Milton Park : Taylor & Francis, 2009) McCord, Jeffrey; Schäfer, Rudolf
    Multiple changes in the internal structure of magnetic domain walls due to alterations of the interfacial coupling across the ferromagnetic/antiferromagnetic interface are reported for Ni81Fe19/NiO exchange coupled films. Depending on the antiferromagnetically induced anisotropy, three different types of domain walls are observed. Cross-tie domain wall structures of decreased vortex to anti-vortex spacing develop with the addition of a thin antiferromagnetic layer. For exchange biased samples strong asymmetries in domain wall structure occur for the ascending and descending branch of the magnetization loop. For the descending branch a symmetric 180° Néel wall develops, whereas a folded cross-tie domain wall structure forms during magnetization reversal along the ascending loop branch. The novel type of 'zig-zagged' cross-tie wall is characterized by cross-ties reaching differently into the surrounding domain areas. The wall alterations indicate the existence of bi-modal coupling strengths in exchange coupled systems, which is in accordance with models of exchange bias that assume pinned and unpinned spins at the ferromagnetic/antiferromagnetic interface.